Pressure-sprayable water-soluble alkyl acrylate polymer solutions



United States Patent 3,305,512 PRESSURE-SPRAYABLE WATER-SOLUBLE ALKYLACRYLATE POLYMER SOLUTIONS Robert J. Gander, Whitehouse, N.J., assignorto Johnson & Johnson, a corporation of New Jersey No Drawing. Filed Apr.9, 1964, Ser. No. 358,643 9 Claims. (Cl. 260-33.2)

The present invention relates to water-soluble filmforming compositionsand more particularly to pressuresprayable solutions of water-solublefilm-forming polymers in which the propellent is the sole solvent forthe film-forming polymer.

Because of the convenience of application, it is becoming increasinglypopular to apply film-forming compositions from pressurized containersin the form of a fine mist or spray. The pressure is obtained byincluding in the container a highly volatile liquid that is a gas atordinary room temperatures and pressures. Because of the insolubility ofmost film-formers in such volatile propellent liquids, it has been thepractice to first prepare a solution of the film-forming polymer in aconventional solvent, such for example as acetone, ethyl acetate, orethanol and then to charge the container with this solution and thepropellent liquids to be used.

These solvents, however, are generally not readily released by thefilm-forming polymer and tend to evaporate relatively slowly.Propellents, on the other hand, although present as liquids in thepressurized container are gases at normal room temperature andaccordingly evaporate rapidly. I have discovered that polymers of alkylacrylates, both homopolymers and copolymers with other monomers, aregenerally soluble in certain propellents, hereinafter called solventpropellents, where the alkyl group is not too small; i.e., where itcontains at least four carbon atoms and where the alkyl acrylate ispresent in amounts of at least 50% by weight of the polymer. However,all solutions of such acrylate and methacrylate polymers will not givesatisfactory sprayable film-forming compositions. Also films formed fromsuch polymers are insoluble in water and, accordingly, where applied toa patient, must either be peeled off or permitted to wear 01f or mustotherwise be removed by the use of organic solvents.

It is an object of the present invention to prepare pressure-sprayablefilm-forming compositions wherein the sole solvent for the film-formingpolymer isthe propellent and in which the film-forming polymer iswatersoluble. It is a further object to prepare pressuresprayablesolutions of water-soluble alkyl acrylate polymers wherein the onlysolvent for the polymer is one of the propellent liquids used and whichwhen released from pressure through a dispensing valve in accordancewith conventional aerosol technique will be dispensed in the form of afine spray or droplets. Other objects and advantages of this inventionwill become apparent from the following description wherein are setforth by way of illustration and example certain embodiments of thesame.

Although the alkyl acrylate polymers are found to be generally solublein propellent solvents where. the alkyl group contains at least fourcarbon atoms and the alkyl acrylate is present in amounts of at least50% by weight of the polymer, these polymers are insoluble in watermaking it necessary to use organic solvents to remove the same afterapplication. It is, as previously indicated, for many uses highlydesirable to have such films waterremovable so that the same, afterbeing formed, can be readily removed by washing with water. Thesepolymers can be made water-removable by including in the acrylatepolymer amine sulfates having the group designated by the generalformula incorporated into the polymer through reaction withdimethylaminoethyl methacrylate hydrosulfate or the free amine which islater converted to the hydrosulfate. The active amine group which formsthe sulfate, should generally be present in amounts of at least 1.0% byWeight of the total acrylate polymer in order to obtainwater-removability of any acrylate polymer film formed. Where the activegroup is present in amounts of much less than 1.0% by weight of theacrylate polymer the desirable characteristic of water-removability willnot be present after the hydrosulfate is formed. The sulfate anion,however, appears to be a relatively active insolubilizing agent insofaras effecting the solubility of the acrylate polymer in propellentsolvent is concerned. With increasing amounts above 2.0% by weight ofI:q H+

in the acrylate polymer the polymer hydrosulfate becomes increasinglyinsoluble in the propellent. Accordingly, in practicing the presentinvention the amine group should be present in amounts within the rangeof about 1.0 to 2.0 based on the weight of the polymer.

The solubilizing amine hydrosulfates are incorporated into the polymerby using preferably, as one of the reactive monomers, dimethylaminoethylmethacrylate. The monomer used may be the amine hydrosulfate. However,in the preferred practice of the invention, the amine hydrosulfates arenot formed until after polymerization has been completed after which theacrylate polymer containing the amine groups is converted to the aminehydrosulfate by neutralization with sulfuric acid.

It is apparently the presence of the amine hydrosulfate which causes thewater solubilizing of the acrylate polymer to the point where films ofthe same can be removed from the skin by washing. It is also thepresence of the dimethylaminoethyl hydrosulfate, when present in toolarge amounts, which inhibits the dissolving of the polymet in thepropellent solvent. Acrylate copolymers containing amine groups arefound to be just as insoluble in Water as acrylate copolymers which donot contain the amine groups and the presence of the amine group doesnot appear to deleteriously affect the solubility in propellentsolvents. However, after the hydrosulfate is formed by incorporating thesulfate ion into the amine group, the acrylate copolymers aresolubilized to the extent that they can be readily removed from the skinby washing with water. However, solubility in the propellent solvent nowno longer occurs if the concentration of the amine group forming thehydrosulfate is above 2.0%. This water group.) However, if theconcentration of the dimethylaminoethyl methacrylate hydrosulfate isincreased to 30% by weight of the polymer, the polymer is no longersufficiently soluble in propellent solvents, such for example as Freon11, to completely dissolve in the same (30% dimethylaminoethylmethacrylate hydrosulfate is equivalent to 2.2% of the vention thefilm-forming polymer is not dissolved in the usual resin solvents but isdissolved in a propellent solvent. The term propellent, as herein used,is used in the conventional sense. A propellent is, for example, definedin Aerosols: Science and Technology," Interscience Publishers, Inc., NewYork, New York, page 214, as A liquefied gas with a vapor pressuregreater than atmospheric pressure (14.7 p.s.i.a.) at a temperature of105 F. This definition is sufficiently broad to include some liquidswhich, used alone, would not function as propellents, but in solutionwith selected liquefied gases make satisfactory pressurized systems. Anexample is methylene chloride whose boiling point is 105 F., at whichtemperature its vapor pressure equals atmospheric pressure. Thus it justfalls within the limits of the definition. At ordinary room temperature,methylene chloride has a vapor pressure below atmospheric pressure andcannot function as a propellent but, when dissolved in a liquid of highvapor pressure, it will give resultant pressures satisfactory forapplication to an aerosol system.

Propellent solvents are those propellents which are also solvents forthe alkyl acrylate film-forming polymers used.

Propellent solvents generally available are trichlorofluoromethane (CClF), generally referred to in the trade group). This is well illustratedby the following table:

ACRYLATE POLYMERS CONTAINING AMINE HYD ROSULFATE GROUPS PolymerComposition, Weight Percent 1 Neut.

Re]. Vis. of Equiv. of Water Solubility Fluoroearbon Free Base 2 FreeBase 3 Solubility 5 EHA BACA DMAEMA 1 EHA=2ethylhexyl acrylate;BACA=N-tert.-butylaerylamide; DMAEMA=Dirnethylaminoethyl mothylaerylate.

2 At a. concentration of 1.000 g./100 ml. in toluene at 30 C.

3 By potentiometric titration in 50-50 benzene-ethanol using 0.1 N

4 At a concentration of 0.2 percent in water.

5 At a concentration of 5.0 percent in 50-50 Propellants 11 and 12.

Although alkyl acrylate polymers and copolymers of the type hereindescribed are found to be soluble in propellent solvents apressure-sprayable solution is not necessarily obtained. Sprayablecompositions or solutions are only obtained if the free base polymerused has a relative viscosity prior to conversion to the salt of notappreciably over 1.60 and is present in solution in the propellentsolvent in a concentration of not appreciably over 6.0 weight percent.As a viscosity of at least about 1.1 is needed in order to form anon-liquid film, the viscosity should preferably be within the range ofabout 1.20 to 1.60. Free base polymer refers to the amine-containingpolymer before conversion to the amine salt. Where the relativeviscosity of the polymer is appreciably greater than about 1.6, or wherethe concentration in the propellent solvent is appreciably above 6.0%, awet jetlike stream is obtained rather than a spray. Relative viscositiesare measured at 30 C. on toluene solutions of the polymer at aconcentration of 1.000 gram per 100 ml.

The alkyl acrylate polymer films are applied by dispensing the sameunder pressure from a pressurized container wherein the polymer ispresent in the form of a solution in one of the propellents used. Thepropellent pressure in the container is preferably in the range of about20 to 60 pounds per square inch gauge at a temperature of 75 F. Wherethe solvent propellent used will not by itself give a sufiiciently hightotal pressure, other propellents are employed together with the solventpropellent to give the pressure desired.

PROPELLENTS As previously indicated, in practicing the presentinethanolic hydrochloric acid.

as Propellent 11; dichlorofiuoromethane (CHCI F), generally referred toin the trade as Propellent 21; vinyl chloride (CH =CHCl); and dimethylether (CH OCH Of these propellent solvents, the one preferred and theone found to give the best results with the widest range of alkylacrylate film-forming polymers is Propellent 11. Propellent 11 is a goodsolvent for the filmforming polymers and is readily released by thepolymers after being dispensed from the pressurized container. WherePropellent 11 is used as the propellent solvent, it is used togetherwith another propellent, such as Propellent 12, dichlorodifluoromethane,in order to increase the pressure in the container to the desired 20 to60 pounds per square inch gauge at 75 F.

With respect to the other propellent solvents referred to, Propellent 21is a good solvent for film-forming resins suitable for use in thepresent invention. This particular propellent solvent, however, has thecharacteristic that it is retained somewhat more tenaciously by thealkyl acrylate polymers than is Propellent 11 even though it boils at asubstantially lower temperature than Propellent 11. This is apparentlydue to the strong associative hydrogen bonding between Propellent 21 andthe resin molecules. Accordingly, for the more rapid drying Propellent11 is preferred.

The vinyl chloride propellent is a good solvent for the alkyl acrylateand alkyl methacrylate polymers.v However, the vinyl chloride propellenthas the charac-- teristic of being retained more tenaciouslyby thedissolved polymer, after the same has been sprayed into a film in muchthe same manner as is Propellent 21. accordingly, gives a much slowerdrying rate for the polymer film despite the fact that the vinylchloride boils.

at +7.9 F. As the vinyl chloride has a gauge pressure of 34 pounds persquare inch at 70 F., it can be used alone without a further propellent.However, the flammable nature of the vinyl choride together with itstendency to be retained by the alkyl acrylate and alkyl methacrylatepolymers makesit generally unsuitable for use alone as the propellentsolvent in the preferred formulations of the present invention.

Dimethyl ether is another fairly good propellant solvent Which is arelatively good solvent for the :alkyl acrylate and alkyl methacrylatepolymers. The dime-thyl ether has a boiling points of 12.7 F. and agauge pressure at 70 F. of 60 pounds per square inch. However, thedi-methyl ether is flammable and has an ethereal odor, both of whichproperties make it generally unsuitable for surgical purposes when usedalone particularly where sparks or open flame may be encountered.

As is clear from the above, the preferred propellent solvent isPropellent 11. The other propellent solvents can, however, be usedparticularly Where used in blends with Propellent 11. They may also, insome instances, be used without any Propellent 11 being present.However, Propellent 11 is preferred, either as the sole propcllentsolvent or as the major propellent solvent where blended with any of theother propellent solvents mentioned. The blending of Propellent 11 withvinyl chloride best illustrates some of the advantages obtained by usingat least some Propellent 11. Vinyl chloride has been indicated as beingflammable and, accordingly, generally undesirable in the preferredcompositions. However, the vinyl chloride can be used in minor amountsin blends with Propellent 11 and non-solvent Propellent 12 to givesatisfactory nonflarnmable propellent compositions. For example, thefollowing formulations are nonflammable and give the indicated pressureat 70 F.

Weight Percent Pressure at 70 F. p.s.i.g. Prop. 11 Prop. 12 ViClPROPELLENT SOLUTION OF FILM-FORMING POLYMER As previously indicated, Ihave discovered that alkyl acrylate polymers are generally soluble inthe propellent solvents, heretofore dis-cussed, where the alkyl groupcontains at least 4 carbon atoms, the larger the alkyl group apparentlythe more readily soluble the polymer. The homopolymers of the alkylacrylates are readily soluble as are generally the copolymers of thesemonomers with other monomers particularly where the alkyl acrylate ispresent in the copolymer in amounts of at least 50 percent by weight ofthe polymer.

The film to be formed may either be a permanently tacky film of thepressure-sensitive adhesive type or a dry protective fihn covering. Thisis controlled by the particular polymer or copolymer used. However,satisfactory propellent solutions of the polymer cannot be obtainedunless the polymer has a relative viscosity of not 6 appreciably over1.60 and is present in the propellent solvent in a concentration of notappreciably over 6.0 weight percent.

Among the preferred polymers for practicing the present invention areterpolymers of an alkyl acrylate, N-tert.- butylacrylamide anddimethylaminoethyl methacrylate hydrosulfate.

Either Z-ethylhexyl acrylate or nabutyl acrylate give excellentfilm-forming resin-s when polymerized with N- tert.-butylacrylamide andthe amine-containing methacrylate, subsequently converting the polymerto the amine hydrosulfate salt. The lower alkyl acrylates, such asmethyl and ethyl, when used in these systems are generallyunsatisfactory for the purposes of the present invention, as thepolymers obtained are not sufliciently soluble in the propellentsolvent.

The effect of concentration of polymer in the propellent solvent is wellillustrated by the following table. This table shows the spraycharacteristics of hydrosulfate salts of two terpolymers. One of theterpolymers contains 70 percent Z-ethylhexyl acrylate, 10 percentN-tert.- butylacrylamide and 20 percent dimethylaminoethyl methacrylate.The other contains 65 percent 2-ethylhexyl acrylate, 10 percentN-tert.-butylacrylamide and 25 percent dimethylarninoethylmethacryla-te. Spray characteristics for both polymeric salts are thesame. The terpolymers are dissolved in a propellent solvent consistingof 50 percent trichlorofluoromethane and 50 percentdichlorodifluoromethane. The ingredients are placed in 6-ounce pressurecans which are closed with conventional aerosol spray nozzles.

Hydrosulfates of terpolymers, wt. percent: Spray character 3.0 Finespray. 5.0 Fine spray. 7.0 Fine spray, but polymer The followingexamples, given for the purpose of illustration only, will help tofurther illustrate the practice of the present invention:

Example I A 5-liter, 3-neck flask is provided with a reflux condenser, amechanical stirrer, a nitrogen inlet tube, and a thermometer. The flaskis charged with 525 grams of Z-ethylhexyl acrylate, 150 grams ofdimethylaminoethyl methacrylate, 75 grams of N-tert.-butylacryla.mideand 750 grams of ethyl acetate. The dirnethylaminoethyl methacrylateamounts to 20 percent of the monomer charge. During a 30-minute periodthe reaction mixture is heated to 7580 C. and stirred while a slowstream of nitrogen is swept through the apparatus. The Ntert.-butylacrylami-de dissolves during this heating period. Nitrogen flow isthen discontinued and 1.90 grams of 2,2'-azobisisobutyronitrile areadded. After an induction period of a few minutes, an exothermicpolymerization takes place, causing the ethyl acetate to refluxvigorously. This soon subsides, and the thickened reaction mixture isstirred and heated at 85 C. for 3.5 hours. The reaction is thendiscontinued and the solution cooled to room temperature. The solidscontent of a sample heated for 5 hours at C. is 50.5 percent.

The ethyl acetate is dried from the polymer by casting the solution in athin film on silicone-coated paper, then drying at F. The polymer isvery tacky and has a relative viscosity of 1.31 (1.000 g./ 100 ml.toluene solution at 30 C.). The neutral equivalent of the polymer is780, measured by titrating samples potentiometrically with 0.1 Nethanolic hydrochloric acid in a solution of 50 percent benzene and 50percent ethanol.

The hydrosulfate salt of the polymer is prepared by neutralizing 100grams of the reaction mixture with 34.0 ml. of 1.90 N ethanolic sulfuricacid. The salt is dried on silicone-coated paper. It is a slightly tackymaterial which dissolves in water at a concentration of 0.2 gram per 100ml. to give a turbid solution. It dissolves at a concentration ofpercent in a blend of 50 percent trichlorofluoromethane and 50 percentdichlorodifluoromethane, forming a colorless solution.

Example II The polymerization procedure of Example I is repeated using amonomer charge of 487.5 grams of 2-ethylhexyl acrylate, 75.0 grams ofN-tert.-butylacrylamide, and 187.5 grams of dimethylaminoethylrnethacrylate. The dimethylaminoethyl rnethacrylate amounts to 25percent of the monomer charge. After polymerization, the reactionmixture has a solids content of 50.6 percent. The polymer has a relativeviscosity of 1.29 and a neutral equivalent of 627.

The hydrosulfate salt is prepared as in Example I, using an appropriateamount of standard sulfuric acid based on the neutral equivalent of 627.

The hydrosulfate salt is soluble in water (0.2 gram per 100 ml.) and ina blend of 50 percent trichlorofluoromethane and 50 percentdichlorodifluoromethane.

Example Ill Solutions of the hydrosulfate salts of Examples I and II aremade in each of the four propellent systems shown in the followingtable. The polymer concentration is three weight percent in each case.The solutions are prepared in aerosol cans and closed with spray valves.

No.: Propellant solvent 1 50% trichlorofiuoromethane-SO%dichlorodifluoromethane. 2 90% vinyl chloride-% trichlorofluoromethane.3 60% dichlorofluoromethane-40% dichlorodifluoromethane. 4 l00% dimethylether.

When discharged through the aerosol valve, each of the solutionsproduces a finely atomized spray of excellent appearance. When appliedto the skin, the propellent solvent evaporates rapidly leaving a thinfilm of the polymer. The polymer film is readily removed by Washing withwater.

Particular embodiments of the invention have been used to illustrate thesame. The invention, however, is not limited to these specificembodiments. In view of the foregoing disclosure, variations ormodifications thereof will be apparent, and it is intended to includewithin the invention all such variations and modifications except as donot come within the scope of the appended claims.

Having thus described my invention, I claim:

1. In a pressurized system for spray application a solution of afilm-forming polymer in propellent the solvent for said polymer in saidsystem consisting essentially of a propellent used in said system thepropellent of said system including at least one propellent solvent ofthe group consisting of trichlorofiuoromethane, difluorochloromethane,vinyl chloride and dimethyl ether, said film-forming polymer being apolymer of an alkyl acrylate and dimethylaminoethyl rnethacrylate saidalkyl acrylate having an alkyl group of at least four carbons and beingpresent in said polymer in an amount of at least 50 percent by weight,said polymer in the free base polymer form having an intrinsic viscosityof not over 1.6 and present in said solution in a concentration of notover 6.0 percent by weight, said polymer containing about 1.0 to 2.0percent by weight of the radical where the radical is present in thesalt form I (-I\IIH)2SO4 2. A pressurized system of claim 1 in which themajor portion of propellent solvent is trichlorofluoromethane.

3. In a pressurized system for spray application a solution of afilm-forming polymer in propellent the solvent for said polymer in saidsystem consisting essentially of a propellent used in said system thepropellent of said system including at least one propellent solvent ofthe group consisting of trichlorofluoromethane, difluorochloromethane,vinyl chloride and dimethyl ether, said film-forming polymer being apolymer of an alkyl acrylate polymerized with dimethylaminoethylrnethacrylate, said alkyl acrylate being at least one of the groupconsisting of 2-ethylhexyl acrylate and n-butyl acrylate and beingpresent in said polymer in an amount of'at least 50 percent by weight,said polymer in the free base polymer form having an intrinsic viscosityof not over 1.6 and present in said solution in a concentration of notover 6.0 percent by weight, said polymer containing about 1.0 to 2.0percent by weight of the radical V where the radical is present in thesalt form 4. In a pressurized system for spray application a solution ofa film-forming polymer in propellent the solvent for said polymer insaid system consisting essentially of a propellent used in said systemthe propellent of said system including at least one propellent solventof the group consisting of trichlorofluoromethane,difluorochloromethane, vinyl chloride and dimethyl ether, saidfilm-forming polymer being a terpolymer of an alkyl acrylate, N-tert.-butylacrylamide and dimethylaminoethyl rnethacrylate said alkyl acrylatehaving an alkyl group of at least four carbons and being present in saidpolymer in an amount of at least 50 percent by weight, said polymer inthe free base polymer form having an intrinsic viscosity of not over 1.6and present in said solution in a concentration of not over 6.0 percentby weight, said polymer containing about 1.0 to 2.0 percent by weight ofthe radical where the radical is present in the salt form 5. Apressurized system of claim 4 in which said alkyl acrylate is at leastone of the group consisting of Z-ethylhexyl acrylate and n-butylacrylate.

6. In a pressurized system for spray application a solution of afilm-forming polymer in propellent, said propellent consistingessentially of 75 to 25 parts by weight of trichlorofiuoromethane and 25to 75 parts by weight of dichlorodifluoromethane, said film-formingpolymer being a terpolymer of an alkyl acrylate, N-tert.-butylacrylamideand dimethylaminoethyl rnethacrylate, said alkyl acrylate having analkyl group of at least four carbons and being present in said polymerin an amount of at least 50 percent by weight, said polymer in the freebase polymer form having an intrinsic viscosity of not over 1.6 andpresent in said solution in a concentration of not over 6.0 percent byweight, said polymer containing about 1.0 to 2.0 percent by weight ofthe radical 9 1% Where the radical is present in the salt form 9. Apressurized system of claim 7 in which the alkyl I acrylate is n-butylacrylate.

(filknhsoa References Cited by the Examiner 5 UNITED STATES PATENTSsalld solutlgln t s mm ig n: s fiveiit for said filrn-f0rm1ng 2,617,78011/1952 Lutz 260 33 8 f g f 6 h-chsaid lkl 2,897,172 7/1959 Maeder 26033,8 pres Sys em 0 c a m 1 W 1 a y 3,062,751 11/1962 Wahlin 167.432

acrylate is at least one of the group consisting of Z-ethylhexylacrylateand nbutylacrylate. 10 MO RI F AN 1 E 8. A pressurized system of claim 7in which the alkyl R S E M "maly xammel' acryla te is Z-ethylhexylacrylate, L. T. JACOBS, Assistant Examiner.

1. IN A PRESSURIZED SYSTEM FOR SPRAY APPLICATION A SOLUTION OF AFILM-FORMING POLYMER IN PROPELLENT THE SOLVENT FOR SAID POLYMER IN SAIDSYSTEM CONSISTING ESSENTIALLY OF A PROPELLENT USED IN SAID SYSTEM THEPROPELLENT OF SAID SYSTEM INCLUDING AT LEAST ONE PROPELLENT SOLVENT OFTHE GROUP CONSISTING OF TRICHLOROFLUOROMETHANE, DIFLUOROCHLOROMETHANE,VINYL CHLORIDE AND DIMETHYL ETHER, SAID FILM-FORMING POLYMER BEING APOLYMER OF AN ALKYL ACRYLATE AND DIMETHYLDAMINOETHYL METHACRYLATE SAIDALKYL ACRYLATE HAVING AN ALKYL GROUP OF AT LEAST FOUR CARBONS AND BEINGPRESENT IN SAID POLYMER IN AN AMOUNT OF AT LEAST 50 PERCENT BY WEIGHT,SAID POLYMER IN THE FREE BASE POLYMER FORM HAVING AN INTRINSIC VISCOSITYOF NOT OVER 1.6 AND PRESENT IN SAID SOLUTION IN A CONCENTRATION OF NOTOVER 6.0 PERCENT BY WEIGHT, SAID POLYMER CONTAINING ABOUT 1.0 TO 2.0PERCENT BY WEIGHT OF THE RADICAL